A mouse device includes a casing, a light-transmissible element and at least one light-emitting element. The casing has an opening. The light-transmissible element is disposed within the casing. A portion of the light-transmissible element is exposed outside the opening of the casing. The light-transmissible element includes plural scattering patterns. The at least one light-emitting element is disposed within the casing and located beside the light-transmissible element. The at least one light-emitting element emits a light beam to an internal portion of the light-transmissible element. After the light beam is transmitted through the plural scattering patterns, the light beam is scattered by the plural scattering patterns, and the scattered light beam is transmitted through the opening of the casing and outputted.